1. Field of the Invention
The present invention relates to flame-retardant resin magnet material that can be used in electrical appliances, building materials, and various other fields, and more particularly to a flame-retardant resin magnet material suitable for use in electrical appliances operated for extended periods of time in high-temperature environments, and to an electron beam adjustment apparatus obtained using this flame-retardant resin magnet material.
2. Description of the Related Art
A wide variety of synthetic resin materials have by now been introduced into our daily lives on a large scale and in a variety of forms. With electrical products, for example, large numbers of components made of synthetic resin materials are used as the constituent parts of such products, both large and small. Most of the synthetic resin materials for such synthetic resin components are organic materials, and are thus flammable and have high calorific value, so when these synthetic resin components are heated more than necessary, they ignite and burn, creating a possibility of major fires.
Television receivers, for example, are equipped with electron beam adjustment apparatus obtained by incorporating a plurality of annular magnets into the neck portion of a color picture tube. These annular magnets are molded from resin magnet materials obtained by adding magnetic powders to resin compositions. Because the electron beam adjustment apparatus are disposed adjacent to power generation units that generated considerable amounts of heat, these annular magnets are sometimes heated beyond the allowable limit, in which case the contained resin may ignite and burn, creating a danger that a fire or the like will occur. It is therefore imperative that flame retardancy be conferred on resin magnet materials, which serve as the molding materials for the annular magnets used in electron beam adjustment apparatus.
As typified by such electron beam adjustment apparatus, the resin magnet materials used in electrical products often must be flame retardant, and this requirement has tended to become progressively more stringent in recent years, with the issue of rendering currently flammable resin magnet materials flame retardant gradually becoming a very important element in terms of designing commercial products. Because various standards (for example, the UL standard in the USA) have been instituted concerning the flame retardancy of resin compositions, resin magnet materials also need to satisfy these standards, and continued efforts aimed at satisfying these standards are being made to achieve flame retardancy in resin magnet materials.
Well-known methods for achieving flame retardancy in flammable synthetic resin materials include (1) adding flame retardants to synthetic resin materials, (2) admixing inorganic fillers into synthetic resin materials, (3) compounding synthetic resin materials and flame-retardant polymers, (4) copolymerizing flame-retardant polymers with synthetic resin materials, and other methods. Bromine- or chlorine-based halogen substances have commonly been selected and used as such flame-retardants, inorganic fillers, flame-retardant polymers, flame-retardant monomers, or the like. Halogen-based substances, while possessing excellent flame retardancy, are also known to produce dioxins and other toxic substances during burning. The environmental impact of the toxic substances produced during burning have recently become a concern, and techniques aimed at enhancing flame retardancy without the use of halogen-based flame retardants are being developed. Such techniques are described, for example, in Unexamined Patent Application (Kokai) 1-201347 (Japanese Unexamined Patent Gazette).
This application discloses a polyolefin-based resin composition whose flame retardancy is enhanced by the addition of a nonhalogen-based flame retardant to ethylene, vinyl acetate, or the like. It is also disclosed that combinations of antimony trioxide with aluminum hydroxide, magnesium hydroxide, and other metal oxide hydrates can be used as such nonhalogen-based flame retardants. According to this technique, resin compositions exhibiting excellent flame retardancy can be obtained without the use of halogen-based substances.
This technique, however, still poses problems when applied to an electron beam adjustment apparatus, which is a typical application for the flame-retardant resin magnet material of the claimed invention.
The first problem is that no study has yet been conducted concerning the effect of a magnetic powder on flame retardancy when this powder is added to the resin composition in question, and that no proof has yet been obtained as to whether a magnetic powder is capable of preserving its stable magnetic characteristics in the presence of such flame retardants.
The second problem is that voids form inside the resin composition or that warping or deformation occurs. Aluminum hydroxide or magnesium hydroxide afford flame retardancy by releasing water (H2O) when heated, but when released at the heating temperature at which annular magnets are molded, this water (H2O) is trapped inside the molding, creating voids, warping, or deformation in the molding.
The issue that can be cited as a third problem is that it is completely unclear whether polyamide resins can be used as base resins, not to mention the fact that no information is yet available concerning the mixing ratios of various flame retardants in cases in which such polyamide resins are used as base resins. Polyamide resins are often used in electrical appliances because of considerations related to wear resistance, machining precision, heat resistance, mechanical strength, and the like, but the aforementioned techniques still cannot be used as reference because of the absence of any mention of the mixing ratios of various flame retardants in cases in which polyamide resins are used as base resins. In these conditions, a need existed for a resin magnet material that would be obtained by employing a polyamide resin as the base resin and that would have excellent flame retardancy and produce moldings devoid of voids, warping, deformation, or the like.
As a result of painstaking research aimed at overcoming the aforementioned problems, the inventors have succeeded in defining the specific aspects that should be adopted when polyamide resins are used as base resins in resin magnet materials obtained using halogen-based flame retardants. As used herein, the term xe2x80x9cspecific aspectsxe2x80x9d primarily refer to the types and mixing ratios of the flame retardants used.
The present invention can be broadly divided into the following three groups.
The inventions belonging to the first group reside in a flame-retardant resin magnet material obtained by adding
(Z) an alnico-based magnetic powder or a ferrite-based magnetic powder to a flame-retardant resin composition that is itself obtained by adding heat-resistant aluminum hydroxide and antimony trioxide to a polyamide resin in the following amounts:
(A) per 100 weight parts polyamide resin,
(B) X1 weight parts heat-resistant aluminum hydroxide with a decomposition temperature of 280xc2x0 C. or higher (where 10 weight parts less than X1 less than 70 weight parts), and
(C) X2 weight parts antimony trioxide (where 40 weight parts less than X2 less than 270 weight parts).
The alnico-based magnetic powder is beneficial because of its less pronounced heat demagnetization, which is a phenomenon in which magnetic characteristics are adversely affected when the temperature rises, whereas the ferrite-based magnetic powder is beneficial because is it inexpensive and readily available.
The inventions belonging to the second group reside in a flame-retardant resin magnet material obtained by adding
(Z) an alnico-based magnetic powder or a ferrite-based magnetic powder to a flame-retardant resin composition that is itself obtained by adding heat-resistant aluminum hydroxide, antimony trioxide, and zinc borate to a polyamide resin in the following amounts:
(A) per 100 weight parts polyamide resin,
(B) X1 weight parts heat-resistant aluminum hydroxide with a decomposition temperature of 280xc2x0 C. or higher (where 10 weight parts less than X1 less than 70 weight parts),
(C) X2 weight parts antimony trioxide (where 40 weight parts less than X2 less than 250 weight parts), and
(D) X3 weight parts zinc borate (where 0 weight part less than X3 less than 20 weight parts).
This claim is different from the inventions of the first group in that zinc borate is added.
Of these flame-retardant resin magnet materials, those obtained using alnico-based magnetic powders as magnetic powders undergo little demagnetization during a temperature increase and possesses stable magnetic characteristics. Because the present flame-retardant resin magnet material is such that a halogen-based system alone is used as the flame retardant, and a polyamide resin (nonhalogen-based substance) is used as the base resin itself, incineration produces very little or no toxic substances.
In addition, a compound having a decomposition temperature of 280xc2x0 C. or higher is used as the heat-resistant aluminum hydroxide. The important point is that the temperature of 280xc2x0 C. is higher than the molding temperature of the annular magnets. The decomposition temperature of a common aluminum hydroxide is about 230xc2x0 C., causing of the H2O decomposed/dehydrated at this temperature to be released. For example, annular magnets are commonly molded at 250-260xc2x0 C., and when the decomposition temperature of aluminum hydroxide is lower than the molding temperature, the H2O released by the endothermic/dehycLration reactions of the aluminum hydroxide enters the molten base resin being molded and accumulates there, causing voids, warping, or deformation to occur in the resulting molding. In the flame-retardant resin magnet material of the present invention, aluminum hydroxide whose decomposition temperature is higher than the molding temperature of the resin composition is selected to avoid this.
The flame-retardant resin magnet material of the present invention exhibits excellent flame retardancy over a wide range of temperatures. This is attributed to the following factors.
The flame-retardant resin magnet materials belonging to the first group are endowed with flame retardancy by the synergy of the flame-retardant effect based on antimony trioxide (Sb2O3) and the flame-retardant effect based on the heat-resistant aluminum hydroxide. Specifically, if heating occurs for any reason and this heating causes the temperature of the flame-retardant resin magnet material to rise to 270xc2x0 C. or above, reactions involving the heat-resistant aluminum hydroxide are first initiated, and burning is prevented by the water (H2O) resulting from the decomposition of the heat-resistant aluminum hydroxide. When the temperature subsequently rises to 450-460xc2x0 C., the heat-resistant aluminum hydroxide stops reacting and the antimony trioxide starts melting. This spreads across the resin surface, creating air-blocking action and preventing burning. Thus, the H2O released by the endothermic/dehydration reactions of the heat-resistant aluminum hydroxide contributes to burning prevention at comparatively low temperatures, and the air-blocking action of the molten antimony trioxide contributes to burning prevention at comparatively high temperatures. As a result, flame retardancy is achieved over the entire temperature range of 270-700xc2x0 C. required by the UL standard.
The flame-retardant resin magnet materials belonging to the second group, in addition to having this action, demonstrate the flame retardant effect provided by the zinc borate. The flame retardant effect of the zinc borate is based on the decomposition-induced heat absorption/dehydration. Care should be exercised in this case because glowing is apt to occur if too much zinc borate has been added.
It is suggested that the following limiting elements be appended as the more-preferred aspects of the first and second groups.
The mixing ratio of the polyamide resin and the alnico-based magnetic powder or ferrite-based magnetic powder should preferably be 50-10 vol % alnico-based magnetic powder or ferrite-based magnetic powder per 50-90 vol % polyamide resin.
A compound having an average particle size r of 1 xcexcm less than r less than 4 xcexcm should be used as the heat-resistant aluminum hydroxide. Flame retardancy is stabilized and productivity improved when the average particle size r of the heat-resistant aluminum hydroxide falls within the range 1 xcexcm less than r less than 4 xcexcm. An r-value that is lower than necessary results in diminished compounding with synthetic resins and in impaired resin fluidity during injection molding because of increased specific surface, with the result that productivity is adversely affected, whereas an r-value that is higher than necessary impairs surface activity and fails to adequately promote decomposition of the heat-resistant aluminum hydroxide, making it impossible to achieve adequate flame retardancy. Both flame retardancy and productivity are adequate, however, when r satisfies the condition 1 xcexcm less than r less than 4 xcexcm.
The flame-retardant resin magnet materials belonging to the third group of the present inventions are as follows.
The flame-retardant resin magnet materials are obtained by adding
(Z) an alnico-based magnetic powder or a ferrite-based magnetic powder to a flame-retardant resin composition that is itself obtained by adding heat-resistant aluminum hydroxide, antimony trioxide, and guanidine sulfamate to a polyamide resin in the following amounts:
(A) per 100 weight parts polyamide resin,
(B) X1 weight parts heat-resistant aluminum hydroxide with a decomposition temperature of 280xc2x0 C. or higher (where 10 weight parts less than X1 less than 70 weight parts),
(C) X2 weight parts antimony trioxide (where 30 weight parts less than X2 less than 170 weight parts), and
(E) X4 weight parts guanidine sulfamate (where 5 weight parts less than X4 less than 20 weight parts).
These flame-retardant resin magnet materials differ from the aforementioned first and second groups in containing guanidine sulfamate.
A flame-retardant resin magnet material belonging to the third group is provided with an excellent flame retardant effect by the respective synergy of the respective flame retardant actions of the heat-resistant aluminum hydroxide, antimony trioxide, and guanidine sulfamate. Specifically, the inert guanidine sulfamate gas inhibits flaming during initial burning; a reaction involving the heat-resistant aluminum hydroxide starts when the temperature rises to 300xc2x0 C.; and burning is prevented by the H2O produced by endothermic/dehydration reactions. When the temperature subsequently rises to 450-460xc2x0 C., the heat-resistant aluminum hydroxide stops reacting and the antimony trioxide starts melting. This spreads across the resin surface, creating air-blocking action and preventing burning. As a result, flame retardancy is achieved over the entire temperature range required by the UL standard. This flame-retardant resin magnet material demonstrates a better flame retardant effect than do the aforementioned materials of the first and second groups as a result of the added action of the inert guanidine sulfamate gas, which suppresses flaming during initial burning.
It is suggested that the following limiting elements be appended as the more-preferred aspects of the inventions of the third group.
The mixing ratios of the flame-retardant resin composition (obtained by adding (B), (C), and (E) to (A) as described above) and the alnico-based magnetic powder or ferrite-based magnetic powder (Z) should preferably be 45-5 vol % alnico-based magnetic powder or ferrite-based magnetic powder per 55-95 vol % flame-retardant resin composition.
When an alnico-based magnetic powder is used as the magnetic powder, 40-80 xcexcm should be selected as the average particle size thereof.
When a ferrite-based magnetic powder is used as the magnetic powder, strontium ferrite or barium ferrite should preferably be employed, and 1.0-3.0 xcexcm should be selected as the average particle size thereof.
Electron beam adjustment apparatus can be fabricated using each of the flame-retardant resin magnet materials broadly divided into the three groups described above. With such electron beam adjustment apparatus, the aforementioned flame-retardant resin magnet materials are used as base materials for the annular magnets incorporated into the electron beam adjustment apparatus, and these flame-retardant resin magnet materials are applicable as some or all of the base materials of quadrupole or sextupole convergence-adjusting magnets or dipole purity-adjuisting magnets.
Such electron beam adjustment apparatus will not ignite or burn when heated as a result of being placed close to a power generation unit, and will produce only negligible amounts of toxic substances if burning does occur. In the particular case of an alnico-based magnetic powder being used as the magnetic powder, a temperature increase produces only a slight reduction in magnetic characteristics (heat demagnetization), making it possible to obtain annular magnets for electron beam adjustment apparatus capable of demonstrating a stable convergence-adjusting effect.